A club-goer killed a 21-year-old with a single slash to the throat in an 'act of pitiless savagery' before going on the run for almost four years, a court heard today.
Shane O'Brien brought a knife to the RE bar in Hillingdon, north west London on October 11 2015.
After a row ensued between him and Joshua Hanson, 21, he produced the weapon and killed him with a 'single slashing motion', the Old Bailey was told.
He went on the run and was finally arrested by police in March this year.
Jurors heard on Monday that O'Brien hid a knife in his designer Canada Goose jacket before 'surreptitiously' reaching for it to kill the victim.
Mr Hanson had been enjoying an evening with friends with 'no difficulties' until O'Brien dealt his 'catastrophic' blow within 10 seconds of the confrontation, jurors heard.
Shane O'Brien brought a knife to the RE bar in Hillingdon, north west London on October 11 2015 when he used it to kill Joshua Hanson, 21 (right), a court heard today
Crime scene: The RE bar in Hillingdon, north west London, is pictured in October 2015 after Mr Hanson's death
Opening the prosecution case, Mark Heywood QC said: 'For reasons that have yet to be fully explained, the defendant stood up, he approached the other man.
'As they spoke briefly, with others around them, the defendant reached for his blade and with a single downward slashing motion, he used it.
'He quite simply cut the throat of the man he was facing.
'You will judge for yourselves how best to categorised that even once you have heard all of the evidence.
'The prosecution will describe it as an act of pitiless savagery.'
He told the jury: 'This case is all about the events that happened at the end of a Saturday night out in a north London bar.
'For most there that night, none of them could have predicted what would happen, so sudden and shocking was it.
O'Brien is pictured in another mugshot
'They had gone out in the company of others for a good time.
'But by two o'clock in the morning that followed one young man lay dead and another, a little older, was